Android chat UX: video viewer, emoji/gif/sticker picker, day separators

docs/android-checklist.md

@@ -63,8 +63,10 @@
 
 ## 8. Медиа и вложения
 - [x] Upload image/video/file/audio
+- [x] Upload/send GIF and sticker attachments
 - [x] Галерея в сообщении (multi media)
 - [x] Media viewer (zoom/swipe/download)
+- [x] Fullscreen video viewer from chat bubbles
 - [x] Единое контекстное меню для медиа
 - [x] Voice playback waveform + speed
 - [x] Audio player UI (не как voice)
@@ -107,6 +109,7 @@
 - [x] Контекстные меню без конфликтов жестов
 - [x] Bottom sheets/dialog behavior consistency
 - [x] Accessibility (TalkBack, dynamic type)
+- [x] Day separators in chat timeline (Сегодня/Вчера/дата)
 
 ## 14. Безопасность
 - [x] Secure token storage (EncryptedSharedPrefs/Keystore)